Cross-pollination is a plant reproduction process where pollen is transferred from the male reproductive organ of one flower to the female reproductive organ of another, enhancing genetic diversity.
Two pea plants – one with round yellow seeds (RRYY) and another with wrinkled green (rryy) seeds produce F1 progeny that have round, yellow (RrYy) seeds. When F1 plants are self-pollinated, which new combination of characters is expected in F2 progeny? How many seeds with these new combinations of characters will be produced when a total 160 seeds are produced in F2 generation? Explain with reason.
Share
When the F1 plants (RrYy) are self-pollinated, the possible combinations of alleles segregating during gamete formation can be determined using the principles of Mendelian genetics. The key is to consider the segregation of alleles during both the formation of gametes and their subsequent combination during fertilization.
The possible combinations of alleles in the F2 generation can be obtained through the multiplication of the individual allele combinations for each gene. The alleles segregate independently during gamete formation, following Mendel’s law of independent assortment.
The genotype of the F1 plants (RrYy) can produce gametes with the following combinations:
• RY
• Ry
• rY
• ry
These gametes can then combine in various ways during fertilization. The possible genotypes in the F2 generation, along with their phenotypic expressions, are as follows:
1. RRYY (round yellow)
2. RRYy (round yellow)
3. RrYY (round yellow)
4. RrYy (round yellow)
5. RRyy (round green)
6. Rryy (round green)
7. rrYY (wrinkled yellow)
8. rrYy (wrinkled yellow)
9. rryy (wrinkled green)
So, there are 9 possible combinations of characters in the F2 generation.
To determine the ratio of these combinations, you can use a Punnett square or the multiplication rule. If you cross RrYy x RrYy, you get a 9:3:3:1 ratio for the phenotypes (round yellow: round green: wrinkled yellow: wrinkled green). This is based on the fact that each gene segregates independently, and the combination of alleles for one gene does not influence the combination for the other gene.
Now, if a total of 160 seeds are produced in the F2 generation, you can calculate the expected number of seeds for each phenotype by multiplying the ratio by the total number of seeds:
• Round Yellow (RY): 9/16 * 160 = 90 seeds
• Round Green (Ry): 3/16 * 160 = 30 seeds
• Wrinkled Yellow (rY): 3/16 * 160 = 30 seeds
• Wrinkled Green (ry): 1/16 * 160 = 10 seeds
So, you would expect 90 round yellow seeds, 30 round green seeds, 30 wrinkled yellow seeds, and 10 wrinkled green seeds in the F2 generation.